Continuous tunnel kiln



Nov. 5, 1935.. P. D'H. DREssLER 2,020,140

CONTINUOUS TUNNEL KILN Filed March 28, 1954 5 Sheets-Sheet, 1

lNvENfroR PH/L/P C17-I. DREsLL-R BY s; AWM

ATTORNEY P. 'Dl-l. DREssLER 2,020,140

CONTINUOUS TUNNEL KILN Filed March 2s, 1954 s sheets-sheet 2 Nov. 5,1935.

P. DH. DREssLE-R 2,020,140

CONTINUOUS TUNNEL KILN Filed March s, 1934 5 sheets-sheet s Nov. 5,1935.

Patented Nov. 5, 1935 UNITED STATES CONTINUOUS TUNNEL KILN Philip dHucDressler, Pittsburgh, Pa., assignor to Swindell Dressler Corporation,Pittsburgh, Pa.,

a corporation of Pennsylvania Application March 28, 1934, Serial No.717,707

` 17 claims. (c1. :z5- 142) The present invention relates to continuoustunnel kilns in which goods, for example ceramic ware to be fired orglazed, are subjected to a heat treatment by advancing them slowlythrough an elongated kiln chamber on a movable hearth formed by the worksupporting platforms of a train of cars extending through the kilnchamber, cars being added to the train at the entrance end of the kilnand being separated from the train at the exit end of the kiln inaccordance with the train movement through the kiln. More specifically,the invention relates to continuous tunnel kilns of the type includingmunie-heating provisions, whereby the burning gases and products ofcombustion formed by the combustion of the fuel burned in heating thekiln, are wholly or largely kept out of the kiln goods space or out ofthe high temperature portion, at least, of said space. y

The general object of the present invention is to improve kiln heatingconditions, and the invention comprises a method of intensifying thesupply of heat to spaces in the bodies of the kiln cars beneath theirwork supporting platforms, by the radiation of heat from the surfaces ofbodies associated with the combustion chambers of the muiiie heatingprovisions. The invention in some of its forms, also provides for anintensification of the heat supply to said car body spaces, by thepassage of heating gases through said spaces from one side of the kilnto its other side. The invention also comprises novel features of kilnconstruction and arrangement whereby the intensified supply of heat tosaid car body spaces is effected. Kilns of the general type abovementioned and having muille heating provisions are well known, and aspecic object of the invention is to secure the desired improvements inheating conditions in kilns which in respect to major features ofconstruction, of the kiln cars as well as the kiln proper, may followthe standard and approved practices of the art.

More specifically stated, the improvements in heating conditions whichit is the main object of the invention to provide, are concerned with anincrease in the rate at which heat is supplied to the kiln car bodies,relative to the rate at which heat is supp'ied to the goods space properof the kiln. In kilns of the type for which the invention is especialyuseful, the kiln cars employed include body portions of a Weight andheat absorbing capacity which are substantial in comparison with,and/are frequently considerably greater than the weight and heatabsorbing capacity, respectively, of the goods supported by the cars. Inthe practical operation of such kilns, each car inserted in the entranceend of the kiln ordinarily has a car body temperature substantiallybelow the temperature to which the goods on the car are to be heated.The proper heating of the goods neces- 5 sarily requires a substantialheating of the car bodies which if their upper or goods platformportions do not heat up as rapidly as the goods which they support,necessarily absorb heat from the goods in the lower portion of the goodsspace of the kiln, and thereby prevent the goods adjacent the carplatforms from heating up uniformly with the goods higher up in thegoods space and less subject to the heat absorbing effect of the carbodies. The invention is especially useful in tunnel kilns of relativelymoderate or small length, and in which the kiln time cycle, i. e. thetime required for the movement of a car through the kiln chamber, isrelatively short, as in such kilns the rate at which the goods areheated up to the maximum goods temperature attained is relatively rapid,and the rapidity of car body heating required for a sufciently uniformgoods heating effect is correspondingly increased. Moreover, in suchkilns, the weight and heat absorbing capacity of the car bodies relativeto the weight and `heat absorbing capacity of the goods is frequently,

and indeed usually, higher than in longer kilns operating with asubstantially longer time cycle.

The present invention comprises and is primarily characterized byprovisions made for heating the car bodies by radiation from the lowerportions of the combustion chambers extending alongside of, andsupplying heat to the high temperature portion of the goods space of thekiln. The invention in some forms of embodiment is further characterizedby and consists in provisions whereby the heating of the car bodies byradiation, as mentioned above, is supplemcnted by a car body heatingeffect due to the movement of heating gases through channels in the carbodies beneath the work supporting platform of the latter.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,however, its advantages a-nd specific objects attained with it,refercnce should be had to the laccompanying drawings and descn'ptivematter in which I have illustrated and described preferred forms ofembodiment of the invention.

Of the drawings.:

Fig. 1 is a plan section of one longitudinal portion, and Fig. 1A is asimilar section of the remaining longitudinal portion, of a tunnel kiln,the section in each figure being taken on the level of the line I-I ofFig. 3;

Fig. 2 is a somewhat diagrammatic representation oi.' means which may beemployed in withdrawing Waste heating gases from the kiln shown in Figs.1 and 1A;

Fig. 3 is a transverse vertical section taken on the broken line 3-3 ofFig. l;

Fig. 4 is a partial sectional elevation on the line 4 4 of Fig. 3;

Fig. 5 is a partialsectional plan taken on the line 5 5 of Fig. 3, andon a larger scale than gFigs. l and 1A;

ing sections A', A2 and A3, respectively, extend" ing in the order namedbetween the entrance and exit end of the kiln. Beneath the goods spaceof the kiln are track rails B for the kiln cars C. Each of the latter asshown comprise a metallic under structure in which the car wheels aremounted, a refractory body portion C', girders C2 extending transverselyof the car and supported on the body C and supporting the goodssupporting platform C4 oi.' the car, the girders C2 being spaced awayfrom one another to provide channels C3 extending horizontally throughthe car structure between the body C' and platform C4. Openings C*s inthe platform C4 permit of! circulation of the kiln atmosphere betweenthe goods space proper, of which the car platforms C4 form the movablebottom wall and the channels C2, which communicate at their ends withspaces between the side edges of the platfonn C4` and the adjacentstationary portions of the kiln structure.

As shown and above described the kiln cars are' of the usual type, andin their general form may be like the cars shown, for example, in myprior patent, 1,521,216 granted December 30, 1924.

The features of kiln construction and arrangement shown in Figs. 1, 1A,3, 4 and 5 follow the usual practice of the art also, in that the carbodies are formed with projecting shoulder portions Cs which coact withadjacent parts of bench portions A4 of the kiln structure to providetortuous passages minimizing the tendency Ito air or gas flow betweenthe level of the tops' of the car bodies and benches, and the spacethrough which the metallic under structures of the car move. Metallicwebs C'z extending longitudinally of the rails B and carried by theupper portions of the metallic car under structures dip into sand filledchannels at the sides of the cars to provide sand seals D against thepassage of gases or air between the goods space and the space throughwhich the car wheels travel. As shown, in the high temperature secticnA2 of the kiln the space last mentioned is open to the atmospherebeneath the bench portions of the kiln.

Above each -bench A4 in the high temperature portion A2 of the kilnthere is a combustion chamber E extending longitudinally of that secingkiln section A'. Suitable provisions are made 5' for effectingcombustion in the combustion chambers E. The heating provisions shown inFigs. 1, 1A. 3 and 4 comprise a plurality of oil burners F extendinginto each combustion chamber E at intervals along the length of thelatter. lo The details of the burner oil and air supply provisions neednot be illustrated as they form no part of the present invention, butmay be and ordinarily are in accordance with the usual practice of thisart. 'I'he burning gases and products 15 of combustion are movedlongitudinally of the combustion chambers and nues E to outlets adjacentthe entrance end of the kiln-connected to a suitable draft creatingmeans which may include an exhaust fan, but as shown consists 20 of astack G3. As shown in Fig. 1, the stack is connected by a duct G2 tooutlets G in the bottom wall of they ilues E, each outlet G beingprovided with an individual adjustable throttling damperG'. 25

The above described gas exhausting provisions may'follow the usualpractices of the art. In particular, they may comprise a single outlet Gfrom each combusti-on chamber extension e adja cent the inlet end of thekiln, or as shown each 30 chamber e may have two outlets G, one adjacentthe entrance end of the kiln and the other more remote therefrom. Insuch case, gases are conveyed from the more remote outlet G to theconduit G2 by a bypass channel g formed in each 35 bench A4. In somecases, such provisions as have been referred to, are desirablysupplemented by special gas discharge provisions hereinafter describedand including features illustrated in Fig. 2. 40

The bottom outer side, and top wall of each combustion chamber E areshown as formed by corresponding portions of the main masonry wallstructure of the kiln chamber. 'I'he inner wall of each combustionchamber E is formed by up- 45 rising hollow tile sections H which restat their lower ends on chambered refractory bodies I. The latter restdirectly on the corresponding bench portion A4 and extend upward fromthev latter to a level slightly below the undersides of 50 the carplatforms C4, which preferably overhang the inner ends of the members Ias shown in Fig. 3.

As shown the tile like wall forming members H are inclined to thevertical and have their 55 upper ends in leaning engagement with a ledgeor shoulder Als extending downward into the corresponding combustionchambery from the crown or roof of the kiln structure. The channels inthe tiles H are open at their upper ends to the portion of the goodsspace between the two combustion chambers adjacent the top of the space.As shown the upper ends of the tiles H are beveled of! to facilitate thecirculation of the kiln atmosphere in streams which enter the tilechannels through inner side wall openings H in the latter adjacent thecar platform levels, and which leave the tile channels at the upper endsof. the latter. vUse of such hollow tile combustion chamber Wall formingmembers is not new with me, but on the contrary is and long lhas been acustomary vfeature of the well known Dressler muilie heated kilns and isdisclosed, for example, in Patents No. 1,170,428, granted February 1,1916, and No. 1,348,488, granted August 3, l1920.

In kilns constructed in accordance withh the present invention, the useof the wall forming tile members H give the same general advantages oi'augmenting and directing the goods space at- *mosphere circulation andoi' protecting the sides of the stack of goods in the cars against undueabsorption of radiant heat from the combustion chambers with resultantlocal overheating of the goods, which have led to the extensive use ofsuch wall forming members as combustion chamber walls in prior tunnelkilns.

The members I are formed with channels or chambers I' which extendtransversely to the length of the kiln and are open at their goods spaceends between the levels of the lower and upper sides of the car bodychannels C3, so that heat may be radiated through each channel I intothe car chemicals C3 and against the adjacent ends of the channelseparating girders C. as the car channel and girder ends successivelymove past said channel I. The heat thus radiatedagainst the upperportion ofthe car structures is radiated mainly by parts P and Io inline with the channels I' Aat the ends of the latter remote from thegoods space. Each part Iz forms a combustion chamber wall partpermanently closing communication between the corresponding combustionchamber E and channel I'. The parts I2 are ordinarily appreciablygreater in number than the parts 12, each of the latter being associatedwith a channel I' between groups of channels I' having their inner endsclosed by parts I2, as shown in Fig. 5. Each part 12 is a body ofrefractory material shaped to serve as a plug valve which in theposition ol the parts 12 shown in full lines in Fig. 5, enters andcloses the end of the corresponding channel I. The latter may be openedfor the ow of heating gases between it and the corresponding combustionchamber, by moving the corresponding part 12 into the combustionchamber, as indicated in dotted lines in Fig. 5, and as shown in Fig. 6.Each part 12 may thus be moved between its channel closing and openingpositions by a suitable implement extended into the com-v bustionchamber through a normally closed opening A formed for the purpose inthe outer wall of the combustion chamber.

The parts I2 may be integral web portions of the corresponding membersI, but advantageously and as shown are in-the form lof thin separately`formed plates, which may be cemented or otherwise permanently securedin place in the corresponding members I, as this makes lt possible toform the parts I2 of silicon carbide or Xother refractory materialhaving a higher thermal conductivity than any material out of which itis ordinarily desirable from the commercial standpoint for use to makethe members I. The high heat conducting capacity of the parts I,

resulting from their thinness and the high ther-V mal conductivity ofmaterial of which they are made, is desirable because it increases thetemperature attained by, and therefore the heat radiating capacity of,the surface of each part I2 which faces and radiates heat through thecorresponding channels I' into the car chanthe part P9 will ordinarily`be such that lthe lat- \ter has less heat conducting capacity than islpossessed by a part I.

To increase the absorption bythe car structures, and particularly by thegoods platforms 5 C4 of the heat which is radiated through the channelsI', I advantageously mount in the lower central portion of each channelC3 a refractory body ,of wedge shape with its apex or sharp edgeuppermost and extending longitudinally of the car body. Each of the twoinclined wedge surfaces C1 of the body'C is thus advantageouslypositioned to receive radiant heat from the adjacent members I or IA,and to reflect or reradiate the'heat so received upward against the l5car platform C* and the upper portions of lthe girders C. lEach body C9may well consist of a single piece of refractory material convenientlyin the form of an inverted trough with closed ends, which is readilyremovable and re- 20 placeable if and-'when desirable. The use of suchbodies C9 in the relation specied is of substantial practicalimportance. It has been found that in the operation of one kiln of thetype illustrated in Figs. 1, 3 and 4, for example, 25 that as the goodstreated are being heated up, the temperature of the goods adjacent thecentral portion'of each car platform averages from 30 to 40 hotter whenthe bodies C9 are in place than when they are removed, with conditionsof 30 operation otherwise the same in each case. Such an increase in thetemperature of the por- `tion of the goods which invariably tends toheat up less rapidly than the rest of the goods, as the latter arebrought up to their maximum temperature, contributes substantially to adesirable uniformity of goods heating, and, in fact increases the kilncapacity by shortening the time cycle required to subject the goods to agiven heat treatment.

Except in respect to special provisions, hereinafter described, whichmay be employed for withdrawing heating gases and regulating thepressures in the lues e, the general construction and arrangement ofthepreheating section A of the kiln may be of any approved formcustomarily employed, or suitable for use, in a kiln of the general typedisclosed. As shown, the iiues e have top, bottom and outer walls formedby the kiln wall structure as are the corresponding walls of thecombustion chamber E. As shown also, the inner wall of each flue isformed by hollow tile members h which may be exactly like the tilemembers H-previously described, except that the members h have theirlower ends extending into engagement with the corresponding benchportions Aof the kiln. and have their bottom side wall openings hbetween the levels of the tops and bottoms of the car channels C3. Asshown, the inner ends of the members h are in leaning engagement withportions A50 projecting toward the goods space from the upper portionsof the side walls of the kiln structure proper. The character of thecooling section A3 of the ,kiln forms no part of the present invention`and may be of any usual or other form suitable for use with the desiredcondition of kiln operation.

With the features of kiln construction and ar- 70 rangement shown inFigs. 1-6, the upper portions of the kiln cars may receive heat not onlyby radiation through the channels I', when desirable, but also as aresult of the flow of heating gases from one combustion chamber E intothe 75 4 otiiwtiirougii` some of the channels I' and, throughcarchannelsA. The special provisions for such flow of heating gasesinclude the prev'iously mentioned members I, all or some of which may beadjusted to permit gas now through the corresponding channels I', andinclude provisions for preventing movement of the heating gases from-the channels C3 linto the goods space above the car platform C4, andinclude provisions for modifying lthe normally maintainedl balancebetween the gas pressures within the combustion chambers'E, so that'when the members I,2 are moved to their open position gases will passinto the channels C3 from one, and will pass from the channels C3 intothe other of those combustion chambers.

In general, also, it is desirable to eliminate the flow obstructingeffect of the bodies C. or to reduce that effect by reducing the heightof the latter, andl as shown in Fig. 6` the bodies C are entirelyremoved, the additional heating effect of the. heating gas ow throughthe channels C3 being then relied upon to more than compensate for theloss of the localized heating action of the members C. n

The provisions illustrated for preventing gas ow between the goods spaceand the kiln chamber portion below the car platform C4 compriserefractory blocks Ca for closing the car platform openings C5, and meansfor maintaining sand seals J between the edges of the car platform C4and the portions of the combustion chamber inner walls formed by thelower ends of the tile members H and the inner ends of the top wall`portions of the members I. The maintenance of such a sand seal J isfacilitated by the fact that the sides of the car platform C4 overhangthe members I.

The'material designated generically as sana which is employed in thesand seals J, is preferably a granular refractory material such ascourse sand or bitstone or fire clay grog, sufficiently coarse so thatthere is no appreciable tendency for it to ily into contact with thegoods or onto the car platforms when displaced. The sand for maintainingthe sand seals J may be supplied through one or more of the channels inthe wall forming tile members H. Usually it is suiiicient to introducesand for the maintenance of the sand seals J through a tile channel ineach combustion chamber wall adjacent the entrance end of the kilnsection A1, but sand for such purpose may be introduced through othertile channels distributed along the length of the section A2 asconditions make desirable. As shown each tile channel through which sandis thus introduced may receive sand through a pipe K extending down thechannel through the kiln roof and connected at its upper end to a sandhopper K provided at its bottom with a slide valve member K? adjustedfor the intermittent or restricted flow of sand through the pipe K.'I'he sand discharged byr the latter collects initially in the lower endof the tile channel and overflows from the latter through thecorresponding tile wall opening H' onto the adjacent ledge formed by theinner end of the top wall of the members I. As shown the upper sides ofthe latter are recessed to form a sand receiving channel I3. Thelongitudinal movement of the car platforms C4 works the seal formingsand longitudinally of said ledge and,'with the arrangement shown willcause some sand spillage oif the inner edge of the ledge, but the rateat which sand is thus wasted from the sand seals J, with the relativelyslow car movement, is quite slow, and the sand wasted does not interferewith the kiln operation. To prevent the sand wasted from the seals Jfrom accumulating on the benches A4, the upper inner corner edges of thelatter may be g54 bevelled off'as indicated at A40 in Fig. 8. Most ofthe waste sand from the seals J eventually works into and assists inmaintaining the lower sand seals D, though the latter may beindependently supplied with sand in the usual man- 10 ner (notillustrated) adjacent the inlet end of the kiln.

Ordinarily the sand seals J need not extend beyond the ends of the kilnsection A', since while this theoretically permits of gas flow be- 15tween the end portions of the goods space and the subjacent portions ofthe kiln chamber and be low the car platform C, longitudinal flowthrough said space is comparatively slow in any event, and with thenormal kiln pressure condi- 20 tions maintained such flow as may occuris ordinarily insignificant and harmless.' Flow in either directionthrough any channel I' may be regulated or prevented by the adjustmentof the corresponding plug damper member 12. 25

When a. kiln of the type shown in Figs. 1-6 is being operated with 'nodischarge of heating gases from either combustion chamber E exceptthrough the usual outlets G, the dampers Gl associated with said outletsare normally adjusted 30 to maintain equal pressures in the combustionchambers E and flues e at the same points along the length of the fluesystem. To induce a ow of gases through the channels I and Cs from onecombustion chamber E into the other when 35 all or some of the members12 are moved into their open position, the pressures in the twocombustion chambers E must be unbalanced. Such unbalance may be effectedby increasing the exhaust suction on one combustion chamber relative tothat on the other and this may advantageously be effected by provisionsof the character illustrated in Figs. 1 and 2.

The means for the purpose illustrated comprise auxiliary outlets g' fromeach ue adjacent the 45 entrance end of the kiln but preferably moreremote from the latter than the duct G3. As shown each outlet g' isconnected to the stack G3 or other exhausting device by pipes G4 and G5,the latter forming the stem of a Y connection of which the twobifurcations are formed by the pipes G4 each of which is connected to acorresponding one of the outlets g. A pivoted damper L is mounted in theconnection for adjustment between two positions, in one of which oneoutlet g is in free communication with the conduit G5 whilecommunication between the other outlet g' and the pipe G5 is cut off. Inthe second position of the damper L, the last mentioned outlet g" is infree communication with the conduit Gf' and stack G3.

Inv order that the flow through the channels C3 between the twocombustion chambers E may alternate in direction at regular intervals,as is obviously desirable from the standpoint of suitable heatinguniformity, means are advantageously provided to shift the damper L backand forth between its positions at regular intervals. Various controlledrelay mechanisms suitable for such use are known. 'I'he meansdiagrammati- 70 cally illustrated in Fig. 2 for the purpose comprise aconstantly running timing motor M which in practice may be a synchronousalternating current motor having a suitably slow speed shaft M. Thelatter carries a cam M2 oscillating a 75 bifurcated lever M3 pivoted atM4 and connected by a link N to the damper L, so that the latter will beadjusted from one operative position to the other at the end of eachhalf turn of the cam M2. The speed of the shaft M' will ordinarily besuch that the damper L will be shifted from one position to another atintervals of 10 or 20 minutes or so.

To thus alternately diminish the pressure in the combustion chamber Eand its extension e relative to the pressure in the other combustionchamber'and its extension, requires, in general, that the normaldischarge outlet G should be throttled somewhat more than is necessaryor desirable when the kiln is operated, as it may be, without suchunbalancing of the pressures in the two combustion chambers E and theirextension ues. i

In some cases, it is practical and desirable to pass heating gasesthrough'the car channels C3 without unbalancing the pressures in thecombustion chambers, and in Figs. 7 and 8, I have illustrated anarrangement for the purpose in which the heating gases passed throughthe car channels C3 are supplied by auxiliary burners O especiallyprovided for the purpose. The burners are distributed at suitableintervals along the length of each combustion chamber E of the kilnshown in Figs. 7 and 8, burning gases and products of combustion fromeach burner being discharged into the open outer end of a correspondingchannel I. As shown in Fig. 8, the channel I' thus utilized for thepassage oi' heating gases is closed against communication with thecorresponding combustion chamber space by a tube or pipe section P ofsuitable refractory material having one end in engagement with thecorresponding member I, and extending outwardly from the latter throughthe lower portion of the corresponding combustion chamber E into theside wall of the kiln structure. At its outer end each pipe section Preceives burning gases discharged by the delivery nozzle or outlet O ofthe corresponding burner O. The burner O includes a gas supply nozzlecoaxial with the outlet O' and terminating in a burner block P whichopens at its outer end into an air supply channel A6 formed in the sidewall of the burner chamber and receiving air for combustion from theexternal atmosphere or preferably from the cooling section A3 of thekiln, as `conditions make desirable. The gas jet discharged by the pipesupply nozzle of each burner O into the burner outlet nozzle entrains ordraws into the latter from the passage A6, the amount of air requiredfor the combustion of the gas. As those skilled in the art willunderstand, kiln heating gas burners of the general type of the burnersO are well known in the art and hence their operation need not befurther explained herein.

The auxiliary burners O at one side of the kiln chamber section .A2alternate with the burners O at the opposite side of the kiln section,and in preferred arrangements each channel C3 receiving burning gases atits outer end from a burner O is in register with a channel I at theopposite side of the kiln having in association therewith a plug valvemember 12 positioned for the suitable inflow into the adjacentcombustion chamber of the heating gases from the burner O in alignmenttherewith at the opposite side of the kiln. For the proper inflow intoeach combustion chamber E of burning gases from the burners O at theopposite side of the kiln, it is not only necessary to properly adjustthe corresponding plug dampers 12, but also to maintain a properpressure in the combustion chamber. 'I'he pressures deslrably maintainedin the two combustion chambers. may be the same, however, and preferablyare the same or approximately the same as the slightly subatmosphericpressure which would ordinarily be maintained in the combustion chambersE if their damper members 11 were not open to receive gases passingthrough the car channels C3.

The alternate direction of heating ow through each car channel C3resulting from its successive movements from a position in which one endof the channel receives gases from an auxiliary 15 burner O at one sideof the kiln into a position in which it receives gases at its oppositeend from an auxiliary burner 0 at the opposite side of the kiln tends toa suitable uniformity in the upper portion of the car structure.

2 The arrangement shown in Figs. 7 and 8 is ob- 0 viously simpler than,and preferable from thc operative standpoint to the arrangementpreviously described, but in general the use of the arrangement shown inFigs. '1 and 8 is restricted to 25 Vnarily kept as small as possible.Moreover low capacity oil burners such as are required for therelatively small heating eiects which the burners O need to supply,vrequire considerable attention to keep them in proper operativecondition. Where gas is employed as the kiln heating fluid,multiplication of the simple burners required is relativelyunobjectionable from either the construction or operation standpoint,small gas burners being easy to maintain in operation. In heating kilnswith gas, it is customary to supply air for the combustion of the gaswhich has been preheated in the cooling zone section of the kiln, andthe combustion chambers are ordinarily operated under pressures belowthe pressure of the atmosphere, so that the use of the auxiliary burnersO as illustrated in Figs. '7 and 8 requires no change in combustionchamber pressure conditions or in the draft regulating provisions usedin connection with the combustion chambers E of the kiln.

While in accordance with the provisions of the statutes, I haveillustrated and described the best form lof embodiment of my inventionnow known to me, it will be apparent to those skilled in the art thatchanges may be made in the form of the apparatus disclosed withoutdeparting from the spirit of my invention as set'forth in the appendedclaims and that in some cases certain features of my invention may beused to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:-

1. In a continuous tunnel kiln, the combination with the kiln chamber,of kiln cars for moving goods through said chamber, said cars havinggoods supporting platforms and spaces beneath said platforms, combustionheating means for heating the goods without contact of the latter withthe heating gases, combustion chambers at the opposite sides of saidkiln chamber, and

bodies of highly heat conducting material associated with said chambersand receiving heat directly therefrom and radiating heat into saidspaces. v

2. In a continuous tunnel kiln, the combination with the kiln chamber,of kiln cars for moving goods through said chamber and each comprising agoods supporting platform and transverse channels beneath said platform,combustion chambers at the opposite sides of said kiln chamber havingthin heat radiating wall portions facing the ends of said channels, andmeans within and extending transversely of said channels adapted toabsorb heat radiated into said channels and to radiate heat upwardagainst the car platforms.

3. In a continuous tunnel kiln, the combination with the kiln chamber ofkiln cars for moving goods through said chamber and each comprising agoods supporting platform and transverse channels beneath said platform,combustion chambers at the opposite sides of said kiln chamber havingthin heat radiating wall portions facing the ends of said channels, andmeans within said channels having heat absorbing and radiating surfacesinclined downwardly and outwardly.

4. In a continuous tunnel kiln, the combination with the kiln chamber,of kiln cars for moving goods through said chamber and each comprising agoods supporting platform, and combustion means for heating the goodswithout contact therewith of the heating gases comprising combustionchambers at the opposite sides of said kiln chamber, each having aninner Wall comprising a portion of relatively low heatradiating'capacity above the car platform level and a portion ofrelatively high heat radiating capacity below said level and facing andadapted to radiate heat into the portion of the cars below saidplatforms. Y

5. In a continuous tunnel kiln, the combination with the kiln chamber,of kiln cars for moving goods through said chamber and each comprising agoods supporting platform, and combustion chambers at the opposite sidesof said kiln chamber, each having an inner wallportion below the carplatform level formed with a set of longitudinally distributed ports anda set of longitudinally distributed thin heat radiating wall partsbetween said ports and adapted to radiate heat into the portions of thecars below said platforms.

6. In a continuous tunnel kiln, the combination with the kiln chamber,of kiln cars for moving goods through said chamber and each comprisingagoods supporting platform and transverse channels beneath saidplatform, and combustion heating means for heating the goods withoutcontact of the latter with the heating gases, combustion chambers at theopposite sides of said kiln chamber having thin heat radiating wallportions facing the ends of said channels and formed of refractoryceramic material of relatively good heat conductivity.

7. In a continuous tunnel kiln, the combination with vthe kiln chamber,of kiln cars for moving goods through said chamber and each comprising agoods supporting platform and transverse channels beneath said platform,and combustion chambers at the opposite sides of said ing goods throughsaid channels and each hav- 5 ing a goods supporting platform andtransverse channels beneath the latter, and combustion chambers atopposite sides of the kiln chamber each including a wall portion at thelevel of said channels formed with openings distributed 10 along thelength of the kiln and thin plates of refractory material of highthermal conductivity extending across said openings.

9. In a continuous tunnel kiln, the combination with the kiln chamber,of kiln cars for mov- 15 ing goods through said chamber and each in`cluding a goods supporting platform and transverse channels beneath thelatter, and combustion chambers at the opposite sides of the kilnchamber having wall portions at the level of 20 said channels havingports therein distributed longitudinally of the kiln and portionsalternating with said ports and radiating heat into said channels.

10. In a continuous tunnel kiln, the combina- 25' tion with the kilnchamber, of kiln cars for moving goods through said chambers and eachcomprising a goods supporting platform and transverse channels beneathsaid platform of kiln, heating means comprising a combustion cham- 30ber at one side of said chamber and having a lower wall portion adjacentand facing the ends of said channels and formed with ports distributedlongitudinally of the kiln and including thin heat radiating portionsbetween said ports. 35 means for effecting combustion within andwithdrawing combustion products from said combustion chambers and meansfor passing hot gases through said channels and ports into saidcombustion chamber. y Y 40 11. In a continuous tunnel kiln, thecombination with the kiln chamber, of kiln` cars for moving goodsthrough said chambers and each comf prising a goods supporting platformand transverse channels beneath said platform of kiln, 45'

heating means comprising a combustion chamber at one side of saidchamber and having a lower wall portion which is adjacent and faces theends of said channels and which is formed with ports distributedlongitudinally of the kiln and 50 which includes thin heat radiatingportions between said ports, means for effecting combustion within saidchamber and for maintaining a pressure therein which is different fromthe pressure in said channels. 55

12. In a continuous tunnel kiln, the combination with the kiln chamber,of kiln cars for moving goods through the kiln chamber and eachcomprising a goods supporting platform and transverse channels beneathsaid platform, kiln 60 heating means comprising combustion chambers ateach side of the kiln chamber and each having a lower wall portionadjacent and facing the adjacent ends of said channels and formed withports distributed iongitudmauy of the kun and 5 including heat radiatingportions alternating with said ports, means for effecting combustionwithin said combustion chambers and means for maintaining differentpressures in said combus- 7o ,tion chamber whereby heating gases willYpass moving goods through the kiln chamber and each comprising a goodssupporting platform and transverse channels beneath said platform, kilnheating means comprising combustion chambers at each side of the kilnchamber and each having a lower wall portion adjacent and facing theadjacent ends of said channels and formed with ports distributedlongitudinally of the kiln and including heatradiating portionsalternating with said ports, means for effecting combustion within saidcombustion chambers and means for periodically modifying the pressuresin said combustion chambers to thereby pass heating gases between saidcombustion chambers through said channels alternately in oppositedirections.

' 14. In a continuous tunnel kiln, the combination with the kilnchamber, of kiln cars for moving goods through said chamber and eachcomprising a goods supporting platform and transverse channels beneathsaid platform, a combustion chamber at each side of said kiln chamberhaving an inner wall portion below the car platform with a set oflongitudinally distributed ports therein adapted to register with thecorresponding ends of the said channels in the cars as the latter areprogressively advanced through the kiln chamber, the ports in each ofsaid wall portions being staggered with respect to those in the otherwall portion, and means at each side of the kiln chamber for passingheating gases into the said ports at the opposite side of the kilnchamber through the corresponding car channels.

15. In a continuous tunnel kiln, the combination with the kiln chamber,of kiln cars for moving goods through said chamber and each comprisinga. goods supporting platform and transverse channels beneath saidplatform, a combustion chamber at each side of said kiln chamber havingan inner wall portion below the car platform with a set oflongitudinally distributed ports therein adapted to register with thecorresponding ends of the said channels lin the cars as the latter areprogressively advanced through the kim chamber, the ports m' each ofsala wan 5 portions being staggered with respect to those in the otherwall portion, andgas burners at each side of the kiln chamber inregister with the said ports at the opposite side of the kiln chamberfor passing heating gases into the last mentioned 10 ports through theintervening car channels.

16. In the operation of a continuous tunnel kiln through which goods aremoved on kiln cars having goods supporting platforms and car body spacesbeneath said platforms, said kiln having 15 combustion chambers at itssides for heating the goods on said platforms, the method ofintensifying the heat supplied to the portions of the goods immediatelyabove said platforms which consists in radiating heat into said car bodyspaces from 20 highly-conducting heat radiating surfaces directlyabsorbing heat from said chambers while preventing the heating gasesfrom coming into contact with the goods.

17. In the operation of a continuous tunnel 25 kiln through which goodsare moved on kiln cars having goods supporting platforms and car bodyspaces beneath said platforms. said kiln having combustion chambers atits sides for heating the goods on said platforms, the method ofintensify- Y9,0 ing the heat supplied to the portions of the' goodsimmediately above said platforms which consists in radiating heat intosaid car body` spaces from highly conducting heat radiating surfacesdirectly absorbing heat from said chambers and passing heating gasesthrough said spaces from a portion of the kiln at one side lof saidspaces to a portion of the kiln at the other side of said spaces.

PHILIP n'noc nnnssmn. o

